The present invention relates to surgical methods and devices and in particular to the percutaneous fixation of a fractured scaphoid bone in the human wrist.
The boat shaped scaphoid bone in the human wrist is the largest bone of the proximal row of the carpus on the lateral (radial) side, articulating with the radius, lunate, capitate, trapezium, and trapezoid. The scaphoid is surrounded on 80% of its surface by joint fluid containing fibrinolysin, a substance that dissolves blood clots.
The scaphoid is frequently fractured in young adults through the mid-portion, or xe2x80x9cwaistxe2x80x9d of the bone. Because blood clots are necessary for the healing of bone fractures, the substantial presence of fibrinolysin around the scaphoid inhibits healing of a fracture of that bone unless the fracture fragments are fixed in sufficiently good apposition that joint fluid is prevented from entering the fracture site. Failure to properly fix the bone fragments into apposition will result in a non-union because of the presence in the fracture site of joint fluid.
In addition to the undesirable non-union result of poor apposition a fracture of the scaphoid through its waist often leads to avascular necrosis or death of the distal pole of the bone. This is because the blood supply to the bone is chiefly through the proximal pole and an unhealed fracture at the bone waist cuts off the blood supply to the distal pole, resulting eventually in severe arthritis and deformity of the wrist.
The traditional conservative treatment of a fractured scaphoid includes the application of a cast to the hand and thumb with the hand in radial deviation in an effort to oppose the fracture ends of the bone. Surgical intervention to fix the scaphoid bone typically includes the use of a Herbert screw which requires the expertise of a hand surgeon specialist and is a tedious and time consuming exposure of the scaphoid bone.
The percutaneous method and the device of the present invention will allow a less experienced hand surgeon or an orthopedist to fix a scaphoid fracture with a lag screw. Such simplification of the procedure leads to good apposition of the bone fragments and an overall improved result, including the minimization of surgical exposure of the wrist.
The present invention provides a simple percutaneous method that incorporates a novel appliance to promote the procedure. The essence of the method is to accurately resolve the required course of a fixation device, such as a lag screw, and to be able to implant the device along the desired course.
The scaphoid bone is disposed in the wrist at an angle that is demonstrated in an anterior-posterior X-ray and at another substantial angle, as demonstrated in a lateral X-ray view of the wrist. Accordingly, it is difficult to insert a fixation device that will truly follow the desired course into the scaphoid bone without substantial surgical intervention or without the aid of an alignment jig, such as the one of the present invention. The apparatus of the present invention comprises a clamp into which the wrist containing the fractured scaphoid is inserted. The clamp fixes the wrist in position so that A-P and lateral view X-rays may be taken. From these X-rays, taken together with radio-opaque alignment markers embedded in the clamp, the desired course of a fixation device may be determined. Resolution of the course includes a determination of the direction and angle of the scaphoid, with respect to the radio-opaque alignment markers, as shown on the A-P view, and measurement of the bone""s angulation, as shown on the lateral X-ray view. Once the course is determined, a jig carried by the clamp is positioned at the distal pole of the scaphoid and is adjusted to align a guide wire with the desired course. Using the aligned jig to support and direct the guide wire, the wire is drilled through percutaneous tissue and into the scaphoid bone along the course and at the angle dictated by the aligning jig.
Once the guide wire is drilled into the bone, the wrist is removed from the clamp. A small longitudinal incision is made in the tissue on either side of the guide wire and that tissue is then spread in order to accommodate the bit of a drill and the lag screw that will be inserted into the bone.
A cannulated drill bit is passed over the guide wire and a hole is drilled to terminate near the proximal end of the scaphoid bone. Following removal of the drill, a cannulated lag screw of appropriate length is passed over the guide wire and screwed into the bone, bringing the fracture fragment faces snugly together in good apposition. The spread tissue is allowed to retract, the guide wire is removed and the incision is closed with a few sutures.
The bone apposition achieved by the accurately placed and well fitted lag screw prevents joint fluid from entering the fracture site and dissolving the blood clots that are necessary for bone union.